The Proceedings of the International Conference on Creationism Volume 4 Print Reference: Pages 283-290 Article 25 1998 Charcoal Bedding as a Tool for Stratigraphic Interpretation Edmond W. Holroyd Follow this and additional works at: https://digitalcommons.cedarville.edu/icc_proceedings DigitalCommons@Cedarville provides a publication platform for fully open access journals, which means that all articles are available on the Internet to all users immediately upon publication. However, the opinions and sentiments expressed by the authors of articles published in our journals do not necessarily indicate the endorsement or reflect the views of DigitalCommons@Cedarville, the Centennial Library, or Cedarville University and its employees. The authors are solely responsible for the content of their work. Please address questions to [email protected]. Browse the contents of this volume of The Proceedings of the International Conference on Creationism. Recommended Citation Holroyd, Edmond W. (1998) "Charcoal Bedding as a Tool for Stratigraphic Interpretation," The Proceedings of the International Conference on Creationism: Vol. 4 , Article 25. Available at: https://digitalcommons.cedarville.edu/icc_proceedings/vol4/iss1/25 CHARCOAL BEDDING AS A TOOL FOR STRATIGRAPHIC INTERPRETATION EDMOND W. HOLROYD, III, PH.D. 8905 W. 63RD AVE. ARVADA, CO 80004-3103 KEYWORDS charcoal, fusain, plant fossils, buoyancy, forest fire, bedding plane, Dakota Formation, Dinosaur Ridge, Colorado ABSTRACT Observations of modern charcoal and sediments at forest fire sites and offossil charcoal in the Dakota For­ mation suggest that the bedding of the charcoal can be an indicator of the speed of the deposition proc­ esses. Buoyancy forces will normally place charcoal and other buoyant materials at bedding planes. Thor­ ough mixing of buoyant plant fragments into sediments indicates catastrophic processes. Lack of redis­ tribution of bedding plane charcoal can indicate rapid burial by subsequent deposits. INTRODUCTION Carbonized plant matter forms a significant part of the stratigraphic record. Coals of various forms have been studied for centuries because of their great economic importance. The coal classification by Stach et a/. (7) includes fusain, or fusinite, which "closely resembles wood charcoal." It is generally a minor part of coals, occurring in lenses with thicknesses in millimeters and lengths in centimeters [6, p.134). The variety named pyrofusinite is attributed to fires followed by bedding in subaquatic environments [6, p.218-219]. Other forms of fusinite arise from bacterial and geochemical action and by plant tissues that were originally black. This paper deals with the presence of charcoal and its fusain likenesses in mod­ ern and ancient sediments rather than the other forms of coal. It also refers to plant matter that has not been carbonized. The vertical distribution, or style of bedding, of the plant matter in the stratigraphic record has become important to creationist studies. Austin (2) studied the deposition of formerly floating logs and root balls at Spirit Lake and found that they can produce a bedding style of upright stumps at multiple elevations after a catastrophic event like the eruption of Mount SI. Helens. That has contributed to a reinterpretation of the fossil forest in Yellowstone Park. Orientation of petrified logs may be indicators of flow direction. Polystrata logs give testimony to generally rapid burial, before plant destruction by weathering and rotting. Preserva­ tion of morphological details in fine shales or volcanic ashes indicates a rapid process but possibly at re­ duced energy levels. Except for surface details, such studies generally involve plant fossils with dimensions in meters. The discussion in this paper refers to plant fragments resembling wood chips with dimensions in centimeters and millimeters. Charcoal in the stratigraphic record can be locally abundant though macroscopic pieces are not a typical component of most sediments. Stach et a/. (7) and Patterson et a/. (6) provide extensive reviews of issues of charcoal generation (fires), transport, deposition, and the properties of resulting materials in the sediments. Their emphasis is on microscopic sizes as in soot and abraded charcoal powder. Williams et a/. [8,9) focus on the properties and presence of large pieces of charcoalized wood in depOSits at Big Bend National Park, Texas. Holroyd [3,4,5) found both macroscopic pieces and impressions of charcoal in the Dakota Formation 283 at Dinosaur Ridge (between Golden and Morrison, Colorado, west of Denver) and elsewhere. He studied the interaction of charcoal and sediments at modem forest fire sites for further understanding. Two styles of bedding were identified. The common and expected type had the charcoal along bedding plane surfaces in thicknesses of millimeters or less, as described by Stach et a/. (7), but laterally extending for many tens of meters. The unusual type had charcoal mixed within the sediments. Buoyancy considerations in those studies indicated that charcoal can be an important tool for interpreting depositional conditions for sedimen­ tary rocks. The mixed style of bedding was attributed to catastrophic depositions of mud flows or slurries or similar geologic processes of very short time span. CHARCOAL PROPERTIES Some of the plant fossils examined by Holroyd at the various Dakota Formation sites varied from powdered carbon to carbon-stained cavities in the rocks to bulk carbon of up to centimeter sizes that was of light den­ sity and had a structural consistency of modem charcoal. Wood grain was visible only in the pieces exceed­ ing millimeter sizes. Another style offossilization had hematite hardening of the walls of cavities and no car­ bon stains or organic remnants. The hematite hardening preserved wood grain more frequently than did the carbon-based fossils. Of particular note were the abundance of wood chip-sized fragments in which the fractures were perpendicular to the wood grain. That is the natural fracture pattem of charcoal as can easily be verified at a forest fire or campfire site. Green wood that is broken by natural forces, such as by a flood, will exhibit frayed ends. Semi-rotten wood can have a range of edge styles depending on the degree of de­ composition. Green and rotten wood are more readily attacked by bacteria and invertebrates than charcoal and may not survive long enough in sediments for preservation of their impressions. The hematite­ hardened fossils were therefore attributed by Holroyd to have been pre-existing charcoal on the basis of the fracture pattem perpendicular to the wood grain. Carbonization of plant matter after burial would not pro­ duce the observed isolated fragments with the perpendicular wood grainlfracture geometries. Charcoal can be buoyant though carbon is not. Air is trapped within charcoal by former cell walls. When dry some forest fire charcoal in my possession will rise to the top of a jar of water within about one second after shaking, floating with as little as one-third of its mass below the water line, thereby indicating a density of about 0.3. When waterlogged it will rise to the top of sediments in a slurry of sand (denSity about 2.6) and water (density 1.0) within about five seconds after agitation. Some charcoal can remain floating at a water­ air surface for over a year while other pieces sink ovemight. Thoroughly wetted or powdered charcoal may have a density of about 1.4. The strength of the buoyant forces upon charcoal indicates that it should most frequently be found at bedding planes in the stratigraphic record: a sediment-water or a sediment-air interface. However, a subsequent flow of water is likely to lift the charcoal from a bedding plane and deposit it downstream unless there are forces, like the drying of mud or entrapment by plant root fibers, bonding the charcoal to the surface of the sediments. Water-soaked charcoal is slightly more dense than water and sinks. Because of its lighter density than other sedimentary particles, water-soaked charcoal is readily sorted and can be concentrated in sedimentary beds. Charcoal concentration (and abrasion to powder) can be observed as a result of wave action at shore­ lines and in similar agitated environments. A striking example of subaqueous accumulation of charcoal is a "fusain clast conglomerate" within the Kentucky No. 12 coal bed. The conglomerate has an area of about 130 km' according to Austin [1 , p.148) and variable thicknesses from 0 to 7 em. Charcoal is sometimes found well-mixed with sediments. Such may be possible in a dry environment in which the carrying fluid, air, is three orders of magnitude less dense than the charcoal or sediments. How­ ever, if water is moving the sediments and charcoal, then the water must be such a minor component of the fluid that there is little opportunity for denSity separation of the materials. This mixing is indicative of cata­ strophic deposition conditions such as a mud flow or density current that move a thick slurry of sediments and charcoal into place. Charcoal is fragile. It is easily crushed by animal traffic and abraded by wind-blown or wave-driven sand. Though generally immune from biological consumption, it is slowly consumed by oxidation at an exposed surface. It readily absorbs water and so it is somewhat vulnerable to fragmentation by repeated freeze-thaw cycles in cold environments. Normally macroscopic pieces of charcoal cannot remain at a dormant surface for centuries awaiting burial by today's slow rates of general deposition. Observing what happens to charcoal at and from a forest fire site can give modem analogs from which we 284 might be able to understand the fossil deposits. The following fire sites were conveniently close enough to the author's home near Denver that they could be repeatedly observed. Sediments generated by torrential runoff from the fire sites were examined for the presence and bedding style of charcoal fragments. All are in mountainous terrain, unlike the supposed coastal plain environment typically envisioned forthe Dakota For­ mation deposition.